US6721106B2 - Taking lens device - Google Patents

Abstract

A optical device has a zoom lens system that is comprised of a plurality of lens units and that achieves zooming by varying unit-to-unit distances and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

Description

This application is based on Japanese Patent Applications Nos. 2000-95247 and 2000-368343, filed on Mar. 29, 2000 and Dec. 4, 2000, respectively, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical device, or a taking lens device. More specifically, the present invention relates to a taking lens device that optically takes in an image of a subject through an optical system and that then outputs the image as an electrical signal, for example, a taking lens device that is used as a main component of a digital still camera, a digital video camera, or a camera that is incorporated in or externally fitted to a device such as a digital video unit, a personal computer, a mobile computer, a portable telephone, or a personal digital assistant (PDA). The present invention relates particularly to a taking lens device which is provided with a compact, high-zoom-ratio zoom lens system.

2. Description of Prior Art

In recent years, as personal computers and other data processing devices have become more and more popular, digital still cameras, digital video cameras, and the like (hereinafter collectively referred to as digital cameras) have been coming into increasingly wide use. Personal users are using these digital cameras as handy devices that permit easy acquisition of image data to be fed to digital devices. As image data input devices, digital cameras are expected to continue gaining popularity.

In general, the image quality of a digital camera depends on the number of pixels in the solid-state image sensor, such as a CCD (charge-coupled device), which is incorporated therein. Nowadays, many digital cameras which are designed for general consumers, boast of high resolution of over a million pixels, and are thus approaching silver-halide film cameras in image quality. On the other hand, even in digital cameras designed for general consumers, zoom capability (especially optical zoom capability with minimal image degradation) is desired, and therefore, in recent years, there has been an increasing demand for zoom lenses for digital cameras that offer both a high zoom ratio and high image quality.

However, conventional zoom lenses for digital cameras that offer high image quality of over a million pixels are usually built as relatively large lens systems. One way to avoid this inconvenience is to use, as zoom lenses for digital cameras, zoom lenses which were originally designed for lens-shutter cameras in which remarkable miniaturization and zoom ratio enhancement have been achieved in recent years. However, if a zoom lens designed for a lens-shutter camera is used unchanged in a digital camera, it is not possible to make good use of the light-condensing ability of the microlenses disposed on the front surface of the solid-state image sensor. This causes severe unevenness in brightness between a central portion and a peripheral portion of the captured image. The reason is that in a lens-shutter camera, the exit pupil of the taking lens system is located near the image plane, and therefore off-axial rays exiting from the taking lens system strike the image plane from oblique directions. This can be avoided by locating the exit pupil away from the image plane, but not without making the taking lens system larger.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an optical, or a taking lens device, which is provided with a novel zoom lens system that, despite being compact, offers both a high zoom ratio and high image quality.

To achieve this object, according to one aspect of the present invention, an optical, or taking lens device is provided with: a zoom lens system that is comprised of a plurality of lens units which achieves zooming by varying the unit-to-unit distances; and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system comprises at least, from the object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power. The zoom lens system achieves zooming by varying the distances between the first to fourth lens units.

According to another aspect of the present invention, an optical, or taking lens device is provided with: a zoom lens system that is comprised of a plurality of lens units which achieves zooming by varying the unit-to-unit distances; and an image sensor that converts an optical image formed by the zoom lens system into an electrical signal. The zoom lens system is comprised of, at least from the object side, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power. The first lens unit comprises a single lens element.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of the present invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanying drawings in which:

FIG. 1 is a lens arrangement diagram of a first embodiment (Example 1) of the invention;

FIG. 2 is a lens arrangement diagram of a second embodiment (Example 2) of the invention;

FIG. 3 is a lens arrangement diagram of a third embodiment (Example 3) of the invention;

FIG. 4 is a lens arrangement diagram of a fourth embodiment (Example 4) of the invention,

FIG. 5 is a lens arrangement diagram of a fifth embodiment (Example 5) of the invention;

FIG. 6 is a lens arrangement diagram of a sixth embodiment (Example 6) of the invention;

FIG. 7 is a lens arrangement diagram of a seventh embodiment (Example 7) of the invention;

FIG. 8 is a lens arrangement diagram of an eighth embodiment (Example 8) of the invention;

FIG. 9 is a lens arrangement diagram of a ninth embodiment (Example 9) of the invention;

FIGS. 10A to 10I are aberration diagrams of Example 1;

FIGS. 11A to 11I are aberration diagrams of Example 2;

FIGS. 12A to 12I are aberration diagrams of Example 3;

FIGS. 13A to 13I are aberration diagrams of Example 4;

FIGS. 14A to 14I are aberration diagrams of Example 5;

FIGS. 15A to 15I are aberration diagrams of Example 6;

FIGS. 16A to 16I are aberration diagrams of Example 7;

FIGS. 17A to 17I are aberration diagrams of Example 8;

FIGS. 18A to 18I are aberration diagrams of Example 9;

FIG. 19 is a diagram schematically illustrating the outline of the optical construction of a taking lens device embodying the invention; and

FIG. 20 is a diagram schematically illustrating the outline of a construction of an embodiment of the invention that could be used in a digital camera.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, optical or taking lens devices embodying the present invention will be described with reference to the drawings and the optical or taking lens device will be referred to as a taking lens device. A taking lens device optically takes in an image of a subject through an optical system and then outputs the image as an electrical signal. A taking lens device is used as a main component of a camera which is employed to shoot a still or a moving picture of a subject, for example, a digital still camera, a digital video camera, or a camera that is incorporated in or externally fitted to a device such as a digital video unit, a personal computer, a mobile computer, a portable telephone, or a personal digital assistant (PDA). A digital camera also includes a memory to store the image from the image sensor. The memory may be removable, for example, a disk, or the memory may be permanently fixed in the camera. FIG. 19 shows a taking lens device comprising, from the object (subject) side, a taking lens system TL that forms an optical image of a subject, a plane-parallel plate PL that functions as an optical low-pass filter or the like, and an image sensor SR that converts the optical image formed by the taking lens system TL into an electrical signal. FIG. 20 shows a zoom lens system ZL, an optical low-pass filter PL, an image sensor SR, processing circuits PC that would include any electronics needed to process the image, and a memory EM that could be used in a digital camera.

In all the embodiments described hereinafter, the taking lens system TL is built as a zoom lens system comprising a plurality of lens units wherein zooming is achieved by moving two or more lens units along the optical axis AX in such a way that their unit-to-unit distances vary. The image sensor SR is realized, for example, with a solid-state image sensor such as a CCD or CMOS (complementary metal-oxide semiconductor) sensor having a plurality of pixels and, by this image sensor SR, the optical image formed by the zoom lens system is converted into an electrical signal. The optical image formed by the zoom lens system has its spatial frequency characteristics adjusted by being passed through the low-pass filter PL that has predetermined cut-off frequency characteristics that are determined by the pixel pitch of the image sensor SR. This helps minimize so-called aliasing noise that appears when the optical image is converted into an electrical signal. The signal produced by the image sensor SR is subjected, as required, to predetermined digital image processing, image compression, and other processing, and is then recorded as a digital image signal in a memory (such as a semiconductor memory or an optical disk) or, if required, transmitted to another device by way of a cable or after being converted into an infrared signal.

FIGS. 1 to 9 are lens arrangement diagrams of the zoom lens system used in a first to a ninth embodiment, respectively, of the present invention, each showing the lens arrangement at the wide-angle end W in an optical sectional view. In each lens arrangement diagram, an arrow mj (where j=1, 2, . . . ) schematically indicates the movement of the j-th lens unit Grj (where j=1, 2, . . . ) and others during zooming from the wide-angle end W to the telephoto end T. Moreover, in each lens arrangement diagram, ri (where i=1, 2, 3, . . . ) indicates the i-th surface from the object side, and a surface ri marked with an asterisk (*) is an aspherical surface. Di (where i=1, 2, 3, . . . ) indicates the i-th axial distance from the object side, though only those which vary with zooming, called variable distances, are shown here.

In all the embodiments, the zoom lens system comprises at least, from the object side, a first lens unit Gr1 having a negative optical power, a second lens unit Gr2 having a negative optical power, and a third lens unit Gr3 having a positive optical power, and achieves zooming by varying the distances between these lens units. In addition, designed for a camera (for example, a digital camera) provided with a solid-state image sensor (for example, a CCD), the zoom lens system also has a glass plane-parallel plate PL, which functions as an optical low-pass filter, disposed on the image-plane side thereof. In all of the embodiments, the first lens unit Gr1 and the glass plane-parallel plate PL are kept stationary during zooming, and the third lens unit Gr3 includes an aperture stop ST at the object-side end thereof.

In the first to the eighth embodiments, the zoom lens system is built as a four-unit zoom lens of a negative-negative-positive-positive configuration. In the ninth embodiment, the zoom lens system is built as a three-unit zoom lens of a negative-negative-positive configuration. In the first to the fifth embodiments, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, the third lens unit Gr3 moves toward the object side, and the fourth lens unit Gr4 moves toward the image side. In the sixth to the eighth embodiments, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, and the third lens unit Gr3 moves toward the object side, but the fourth lens unit Gr4, i.e. the last lens unit, remains stationary together with the glass plane-parallel plate PL. In the ninth embodiment, during zooming from the wide-angle end W to the telephoto end T, the second lens unit Gr2 first moves toward the image side and then makes a U-turn to go on to move toward the object side, and the third lens unit Gr3 moves toward the object side.

In all of the embodiments, the first and second lens units Gr1, Gr2 are given negative optical powers. This makes it easy to build a retrofocus-type arrangement. In a digital camera, the taking lens system TL needs to be telecentric toward the image side and, by building a retrofocus-type arrangement with the negatively-powered first and second lens units Gr1, Gr2, it is possible to make the entire optical system telecentric easily. Moreover, by distributing the negative optical power needed in a retrofocus-type arrangement between the two lens units Gr1, Gr2, it is possible to keep the first lens unit Gr1 stationary during zooming. Keeping the first lens unit Gr1 stationary is advantageous in terms of lens barrel design, so that it is possible to simplify the lens barrel construction and thereby reduce the cost of the zoom lens system.

In the first, the second, and the sixth to the ninth embodiments, the first lens unit Gr1 comprises a single lens element. By comprising the first lens unit Gr1 as a single lens element, it is possible to reduce the cost of the zoom lens system by reducing the number of its constituent lens element. Moreover, comprising the first lens unit Gr1 out of a single lens element helps increase flexibility in the design of lens barrels so that it is possible to simplify the lens barrel construction and thereby reduce the cost of the zoom lens system. On the other hand, in the third to the fifth embodiments, the first lens unit Gr1 comprises two lens elements. This makes correction of relative decentered aberration possible and is thus advantageous in terms of optical performance.

In all of the embodiments, it is preferable that the zoom lens system, starting with either a negative-negative-positive or a negative-negative-positive-positive configuration, fulfill the conditions described one by one below. Needless to say, those conditions may be fulfilled singly to achieve the effects and advantages associated with the respective conditions fulfilled, but fulfilling as many of them as possible is further preferable in terms of optical performance, miniaturization, and other aspects.

It is preferable that conditional formula (1) below be fulfilled.

0.5<f1/f2<5  (1)

wherein

f1 represents the focal length of the first lens unit Gr1; and

f2 represents the focal length of the second lens unit Gr2.

Conditional formula (1) defines the preferable ratio of the focal length of the first lens unit Gr1 to that of the second lens unit Gr2. If the lower limit of conditional formula (1) were to be transgressed, the focal length of the first lens unit Gr1 would be too short. This would cause such a large distortion (especially a negative distortion on the wide-angle side) that it would be impossible to secure satisfactory optical performance. By contrast, if the upper limit of conditional formula (1) would be transgressed, the focal length of the first lens unit Gr1 would be too long. This would make the negative optical power of the first lens unit Gr1 so weak that the first lens unit Gr1 would need to be made larger in diameter, which is undesirable in terms of miniaturization.

It is preferable that conditional formula (2) below be fulfilled.

1.5<|f12/fw|<4  (2)

where

f12 represents the composite focal length of the first and second lens units Gr1, Gr2 at the wide-angle end W; and

fw represents the focal length of the entire optical system at the wide-angle end W.

Conditional formula (2) defines the preferable condition to be fulfilled by the composite focal length of the first and second lens units Gr1, Gr2 at the wide-angle end W. If the upper limit of conditional formula (2) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be too long, and thus the total length of the entire optical system would be too long. Moreover, the composite negative power of the first and second lens units Gr1, Gr2 would be so weak that these lens units would need to be made larger in external diameter. Thus, it would be impossible to make the zoom lens system compact. By contrast, if the lower limit of conditional formula (2) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be too short. This would cause such a large negative distortion in the first and second lens units Gr1, Gr2 at the wide-angle end W that it would be difficult to correct the distortion.

It is preferable that conditional formula (3) below be fulfilled, and it is further preferably fulfilled together with conditional formula (2) noted previously.

0.058<(tan ωw)² ×fw/TLw<0.9  (3)

where

tan ωw represents the half view angle at the wide-angle end W;

fw represents the focal length of the entire optical system at the wide-angle end W; and

TLw represents the total length (i.e. the distance from the first vertex to the image plane) at the wide-angle end W.

Conditional formula (3) defines the preferable relation between the view angle and the total length at the wide-angle end W. If the upper limit of conditional formula (3) were to be transgressed, the optical power of the individual lens units would be too strong, and thus it would be difficult to correct the aberration that occurs therein. By contrast, if the lower limit of conditional formula (3) were to be transgressed, the total length would be too long, which is undesirable in terms of miniaturization.

It is preferable that conditional formula (4) below be fulfilled, and it is further preferably fulfilled together with conditional formula (2) noted previously.

10<TLw×Fnt/(fw×tan ωw)<50  (4)

where

TLw represents the total length (i.e., the distance from the first vertex to the image plane) at the wide-angle end W;

Fnt represents the f-number (FNO) at the telephoto end T;

fw represents the focal length of the entire optical system at the wide-angle end W; and

tan ωw represents the half view angle at the wide-angle end W.

Conditional formula (4) defines the preferable relation between the total length at the wide-angle end W and the f-number at the telephoto end T. If the upper limit of conditional formula (4) were to be transgressed, the total length at the wide-angle end W would be too long, which is undesirable in terms of miniaturization. By contrast, if the lower limit of conditional formula (4) were to be transgressed, the f-number at the telephoto end T would be too low, and thus it would be difficult to correct the spherical aberration that would occur in the third lens unit Gr3 in that zoom position.

It is preferable that the third lens unit Gr3 comprises, as in the first to the fifth and the ninth embodiments, of at least two positive lens elements and one negative lens element. Moreover, it is further preferable that, as in all of the embodiments, the third lens unit Gr3 have an aspherical surface at the image-side end thereof. Let the maximum effective optical path radius of an aspherical surface be Ymax, and let the height in a direction perpendicular to the optical axis be Y. Then, it is preferable that the aspherical surface disposed at the image-side end of the third lens unit Gr3 fulfill conditional formula (5) below at Y=0.7Ymax, and further preferably for any height Y in the range 0.1Ymax≦Y≦0.7Ymax.

−0.6<(|X|−X0|)/[C0·(N′−N)·f3]<0  (5)

where

X represents the surface shape (mm) of the aspherical surface (i.e. the displacement along the optical axis at the height Y in a direction perpendicular to the optical axis of the aspherical surface);

X0 represents the surface shape (mm) of the reference spherical surface of the aspherical surface (i.e. the displacement along the optical axis at the height Y in a direction perpendicular to the optical axis of the reference spherical surface);

C0 represents the curvature (mm⁻¹) of the reference spherical surface of the aspherical surface;

N represents the refractive index for the d-line of the object-side medium of the aspherical surface;

N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface; and

f3 represents the focal length (mm) of the third lens unit Gr3.

Here, the surface shape X of the aspherical surface, and the surface shape X0 of its reference spherical surface are respectively given by formulae (AS) and (RE) below.

X=(C0·Y ²)/(1+{square root over (1−ε·C0² ·Y ²)})+Σ( Ai·Y ⁱ)   (AS)

X0=(C0·Y ²)/(1+{square root over (1−C0² ·Y ²)}  (RE)

where

C0 represents the curvature (mm⁻¹) of the reference spherical surface of the aspherical surface;

Y represents the height in a direction perpendicular to the optical axis;

ε represents the quadric surface parameter; and

Ai represents the aspherical surface coefficient of order i.

Conditional formula (5) dictates that the aspherical surface be so shaped as to weaken the positive power within the third lens unit Gr3, and thus defines the preferable condition to be fulfilled to ensure proper correction of spherical aberration from the middle-focal-length region M to the telephoto end T. If the upper limit of conditional formula (5) were to be transgressed, spherical aberration would incline too much toward the under side. By contrast, if the lower limit of conditional formula (5) were to be transgressed, spherical aberration would incline too much toward the over side.

It is preferable that, as in all of the embodiments, the zoom unit disposed closest to the image plane have a positive power, and it is preferable that the zoom unit having this positive power comprises at least one positive lens element. In cases, as in the first, the fourth, and the sixth to the eighth embodiments, where this zoom unit having the above-mentioned positive power comprises a single positive lens element, it is preferable that this positive lens element fulfill conditional formula (6) below.

0.05<(CR1−CR2)/(CR1+CR2)<5  (6)

where

CR1 represents the radius of curvature of the object-side surface; and

CR2 represents the radius of curvature of the image-side surface.

Conditional formula (6) defines the preferable shape of the positive lens element included in the zoom unit disposed closest to the image plane. If the upper limit of conditional formula (6) were to be transgressed, the surface of this positive lens element facing the object would be highly concave, and therefore, to avoid interference with the lens unit disposed on the object side of that surface, it would be necessary to secure a wide gap in between. This is undesirable in terms of miniaturization. By contrast, if the lower limit of conditional formula (6) were to be transgressed, the positive optical power of the object-side surface of the positive lens element would be so strong that it would be difficult to correct the aberration that would be caused by that surface.

It is preferable that the first to third lens units Gr1 to Gr3 fulfill conditional formula (7) below.

0.4<|f12/f3|<1.5  (7)

where

f12 represents the composite focal length of the first and second lens units Gr1, Gr2, at the wide-angle end W; and

f3 represents the focal length (mm) of the third lens unit Gr3.

Conditional formula (7) defines the preferable ratio of the composite focal length of the first and second lens units Gr1, Gr2 to the focal length of the third lens unit Gr3. If the upper limit of conditional formula (7) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be relatively too long. Thus, if the upper limit of conditional formula (7) were to be transgressed, the exit pupil would be located closer to the image plane, and this is not desirable. As described earlier, in a digital still camera or the like, the use of a CCD and other factors require that rays striking the image plane be telecentric, and therefore it is preferable that the exit pupil be located closer to the object. By contrast, if the lower limit of conditional formula (7) were to be transgressed, the composite focal length of the first and second lens units Gr1, Gr2 would be relatively too short. Thus, if the lower limit of conditional formula (7) were to be transgressed, it would be difficult to correct the negative distortion that would occur in the first and second lens units Gr1, Gr2.

In all of the illustrated embodiments, all of the lens units are comprised solely of refractive lenses that deflect light incident thereon by refraction (i.e. lenses of the type that deflect light at the interface between two media having different refractive indices). However, any of these lens units may include, for example, a diffractive lens that deflects light incident thereon by diffraction, a refractive-diffractive hybrid lens that deflects light incident thereon by the combined effects of refraction and diffraction, a gradient-index lens that deflects light incident thereon with varying refractive indices distributed in a medium, or a lens of any other type.

In any of the embodiments, a surface having no optical power (for example, a reflective, refractive, or diffractive surface) may be disposed in the optical path so that the optical path is bent before, after, or in the midst of the zoom lens system. Where to bend the optical path may be determined to suit particular needs. By bending the optical path appropriately, it is possible to make a camera apparently slimmer. It is even possible to build an arrangement in which zooming or the collapsing movement of a lens barrel does not cause any change in the thickness of a camera. For example, by disposing a mirror after the first lens unit Gr1, which is kept stationary during zooming, so that the optical path is bent by 90° by the reflecting surface of the mirror, it is possible to keep the front-to-rear length of the zoom lens system constant and thereby make a camera slimmer.

In all of the embodiments, an optical low-pass filter having the shape of a plane-parallel plate PL is disposed between the last surface of the zoom lens system and the image sensor SR. However, as this low-pass filter, it is also possible to use a birefringence-type low-pass filter made of quartz or the like having its crystal axis aligned with a predetermined direction, a phase-type low-pass filter that achieves the required optical cut-off frequency characteristics by exploiting diffraction, or a low-pass filter of any other type.

PRACTICAL EXAMPLES

Hereinafter, practical examples of the construction of the zoom lens system used in taking lens devices embodying the present invention will be presented in more detail with reference to their construction data, aberration diagrams, and other data. Examples 1 to 9 presented below correspond respectively to the first to ninth embodiments described hereinbefore, and the lens arrangement diagrams (FIGS. 1 to 9) showing the lens arrangement of the first to the ninth embodiments apply also to Examples 1 to 9, respectively.

Tables 1 to 9 list the construction data of Examples 1 to 9, respectively. In the construction data of each example, ri (i=1, 2, 3, . . . ) represents the radius of curvature (mm) of the i-th surface from the object side, di (i=1, 2, 3, . . . ) represents the i-th axial distance (mm) from the object side, and Ni (i=1, 2, 3, . . . ) and νi (i=1, 2, 3, . . . ) respectively represent the refractive index (Nd) for the d-line and the Abbe number (νd) of the i-th optical element from the object side. A surface whose radius of curvature ri is marked with an asterisk (*) is an aspherical surface, of which the surface shape is defined by formula (AS) noted earlier. Moreover, in the construction data, for each of those axial distances that vary with zooming (i.e. variable aerial distances), three values are given that are, from left, the axial distance at the wide-angle end W (the shortest-focal-length end), the axial distance in the middle position M (the middle-focal-length position), and the axial distance at the telephoto end T (the longest-focal-length end). Also listed are the focal length f, (in mm), the f-number FNO, and the view angle (2ω, °) of the entire optical system in those three focal-length positions W, M, and T, and the aspherical surface data. Table 10 lists the values of the conditional formulae as actually observed in Examples 1 to 9.

FIGS. 10A-10I, 11A-11I, 12A-12I, 13A-13I, 14A-14I, 15A-15I, 16A-16I, 17A-17I, and 18A-18I are aberration diagrams of Examples 1 to 9, respectively. Of these diagrams, FIGS. 10A-10C, 11A-11C, 12A-12C, 13A-13C, 14A-14C, 15A-15C, 16A-16C, 17A-17C, and 18A-18C show the aberration observed at the wide-angle end W, FIGS. 10D-10F, 11D-11F, 12D-12F, 13D-13F, 14D-14F, 15D-15F, 16D-16F, 17D-17F, and 18D-18F show the aberration observed in the middle position M, and FIGS. 10G-10I, 11G-11I, 12G-12I, 13G-13I, 14G-14I, 15G-15I, 16G-16I, 17G-17I, and 18G-18I show the aberration observed at the telephoto end T. Of these diagrams, FIGS. 10A, 10D, 10G, 11A, 11D, 11G, 12A, 12D, 12G, 13A, 13D, 13G, 14A, 14D, 14G, 15A, 15D, 15G, 16A, 16D, 16G, 17A, 17D, 17G, 18A, 18D, and 18G show spherical aberration, FIGS. 10B, 10E, 10H, 11B, 11E, 11H, 12B, 12E, 12H, 13B, 13E, 13H, 14B, 14E, 14H, 15B, 15E, 15H, 16B, 16E, 16H, 17B, 17E, 17H, 18B, 18E, and 18H show astigmatism, and FIGS. 10C, 10F, 10I, 11C, 11F, 11I, 12C, 12F, 12I, 13C, 13F, 13I, 14C, 14F, 14I, 15C, 15F, 15I, 16C, 16F, 16I, 17C, 17F, 17I, 18C, 18F, and 18I show distortion. In these diagrams, Y′ represents the maximum image height (mm). In the diagrams showing spherical aberration, a solid line d, a dash-and-dot line g, and a dash-dot-dot line c show the spherical aberration for the d-line, for the g-line, and for the c-line, respectively, and a broken line SC shows the sine condition. In the diagrams showing astigmatism, a broken line DM and a solid line DS represent the astigmatism for the d-line on the meridional plane and on the sagittal plane, respectively. In the diagrams showing distortion, a solid line represents the distortion (%) for the d-line.

TABLE 1
Construction Data of Example 1
f = 4.45˜7.8˜12.7, FNO = 2.84˜2.84˜2.90,
2ω = 75.8˜46.8˜28.9

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 18.401
		d1 = 0.800	N1 = 1.54072	ν1 = 47.22
	r2 = 5.940

d2 = 3.275˜6.628˜5.000

	r3* = −46.268
		d3 = 0.800	N2 = 1.52200	ν2 = 52.20
	r4* = 7.744
		d4 = 1.115
	r5 = 10.618
		d5 = 1.784	N3 = 1.84666	ν3 = 23.82
	r6 = 29.518

d6 = 14.440˜6.151˜2.201

	r7 = ∞(ST)
		d7 = 0.600
	r8 = 10.096
		d8 = 1.673	N4 = 1.75450	ν4 = 51.57
	r9 = 35.493
		d9 = 0.100
	r10 = 6.646
		d10 = 2.391	N5 = 1.75450	ν5 = 51.57
	r11 = 42.505
		d11 = 0.436
	r12 = 372.791
		d12 = 0.800	N6 = 1.84666	ν6 = 23.82
	r13 = 5.188
		d13 = 0.800
	r14 = 6.476
		d14 = 2.091	N7 = 1.52200	ν7 = 52.20
	r15* = 43.112

d15 = 1.283˜8.292˜13.780

	r16* = −50.000
		d16 = 2.639	N8 = 1.75450	ν8 = 51.57
	r17* = −9.674

d17 = 2.774˜0.700˜0.790

	r18 = ∞
		d18 = 2.000	N9 = 1.51680	ν9 = 64.20
	r19 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.66858 × 10−3, A6 = −0.25227 × 10−4,

A8 = 0.41627 × 10−6

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = 0.27983 × 10−3, A6 = −0.33808 × 10−4,

A8 = 0.43681 × 10−6

Aspherical Surface Data of Surface r15

ε = 1.0000, A4 = 0.14395 × 10−2, A6 = 0.21710 × 10−4,

A8 = 0.13202 × 10−5

Aspherical Surface Data of Surface r16

ε = 1.0000, A4 = −0.39894 × 10−3, A6 = −0.41378 × 10−4,

A8 = 0.19806 × 10−5

Aspherical Surface Data of Surface r17

ε = 1.0000, A4 = 0.27510 × 10−3, A6 = −0.46341 × 10−4,

A8 = 0.17216 × 10−5

TABLE 2
Construction Data of Example 2
f = 4.45˜7 8˜12.7, FNO = 2.67˜2.90˜2.90,
2ω = 76.9˜46.6˜28.5

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 12.628
		d1 = 1.000	N1 = 1.58913	ν1 = 61.25
	r2 = 5.734

d2 = 3.800˜6.823˜4.759

	r3* = −17.691
		d3 = 0.800	N2 = 1.52200	ν2 = 52.20
	r4* = 8.550
		d4 = 1.669
	r5 = 14.585
		d5 = 1.500	N3 = 1.84666	ν3 = 23.78
	r6 = 75.547

d6 = 12.939˜5.191˜1.490

	r7 = ∞(ST)
		d7 = 0.600
	r8 = 10.478
		d8 = 1.730	N4 = 1.78831	ν4 = 47.32
	r9 = 48.647
		d9 = 0.100
	r10 = 5.925
		d10 = 2.491	N5 = 1.58913	ν5 = 61.25
	r11 = 20.627
		d11 = 0.010	N6 = 1.51400	ν6 = 42.83
	r12 = 20.627
		d12 = 0.700	N7 = 1.84666	ν7 = 23.78
	r13 = 4.609
		d13 = 0.632
	r14 = 4.757
		d14 = 2.626	N8 = 1.52200	ν8 = 52.20
	r15* = 14.654

d15 = 1.439˜7.835˜13.100

	r16* = −50.000
		d16 = 1.000	N9 = 1.58340	ν9 = 30.23
	r17* = 70.535
		d17 = 0.591
	r18 = −94.053
		d18 = 1.802	N10 = 1.78590	ν10 = 43.93
	r19 = −8.643

d19 = 2.371˜0.700˜1.200

	r20 = ∞
		d20 = 2.000	N11 = 1.51680	ν11 = 64.20
	r21 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.56623 × 10−3, A6 = −0.23264 × 10−4,

A8 = 0.30123 × 10−6

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = 0.43838 × 10−4, A6 = −0.28329 × 10−4,

A8 = 0.33275 × 10−6

Aspherical Surface Data of Surface r15

ε = 10000, A4 = 0.21324 × 10−2, A6 = 0.32366 × 10−4,

A8 = 0.53566 × 10−5

Aspherical Surface Data of Surface r16

ε = 1.0000, A4 = 0.95453 × 10−3, A6 = −0.13928 × 10−3,

A8 = 0.43729 × 10−5

Aspherical Surface Data of Surface r17

ε = 1.0000, A4 = 0.20120 × 10−2, A6 = −0.13956 × 10−3,

A8 = 0.38295 × 10−5

TABLE 3
Construction Data of Example 3
f = 4.45˜7.8˜12.7, FNO = 2.70˜2.84˜2.89,
2ω = 76.6˜46.4˜29.1

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 11.274
		d1 = 1.000	N1 = 1.74330	ν1 = 49.22
	r2 = 5.143
		d2 = 3.500
	r3* = 302.871
		d3 = 1.800	N2 = 1.52200	ν2 = 52.20
	r4* = −39.780

d4 = 1.500˜3.907˜1.412

	r5 = −20.000
		d5 = 0.800	N3 = 1.63854	ν3 = 55.45
	r6 = 10.669
		d6 = 0.800
	r7 = 12.450
		d7 = 1.550	N4 = 1.84666	ν4 = 23.78
	r8 = 48.662

d8 = 10.824˜3.774˜1.000

	r9 = ∞(ST)
		d9 = 0.600
	r10 = 11.059
		d10 = 1.807	N5 = 1.77250	ν5 = 49.77
	r11 = 137.002
		d11 = 0.100
	r12 = 7.339
		d12 = 2.800	N6 = 1.75450	ν6 = 51.57
	r13 = −37.431
		d13 = 0.010	N7 = 1.51400	ν7 = 42.83
	r14 = −37.431
		d14 = 0.712	N8 = 1.84666	ν8 = 23.78
	r15 = 6.744
		d15 = 1.282
	r16 = 9.773
		d16 = 1.500	N9 = 1.52200	ν9 = 52.20
	r17* = 33.228

d17 = 1.112˜7.313˜12.854

	r18* = 22.508
		d18 = 1.000	N10 = 1.58340	ν10 = 30.23
	r19* = 8.706
		d19 = 0.773
	r20 = 53 706
		d20 = 1.801	N11 = 1.78590	ν11 = 43.93
	r21 = −10.576

d21 = 2.530˜0.971˜0.700

	r22 = ∞
		d22 = 2.000	N12 = 1.51680	ν12 = 64.20
	r23 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.28635 × 10−3, A6 = 0.15667 × 10−4,

A8 = −0.57168 × 10−6

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = −0.17053 × 10−3, A6 = 0.80129 × 10−5,

A8 = −0.94476 × 10−6

Aspherical Surface Data of Surface r17

ε = 1.0000, A4 = 0.14359 × 10−2, A6 = 0.19756 × 10−4,

A8 = 0.24320 × 10−5

Aspherical Surface Data of Surface r18

ε = 1.0000, A4 = −0.14772 × 10−2, A6 = −0 28230 × 10−4,

A8 = 0.39925 × 10−5

Aspherical Surface Data of Surface r19

ε = 1.0000, A4 = −0.12532 × 10−2, A6 = −0.15384 × 10−4,

A8 = 0.28984 × 10−5

TABLE 4
Construction Data of Example 4
f = 4.45˜7.8˜12.7, FNO = 2.88˜2.81˜2.90,
2ω = 76.7˜46˜28.9

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 12.938
		d1 = 1.000	N1 = 1.74330	ν1 = 49.22
	r2 = 5.796
		d2 = 3.500
	r3* = 44.528
		d3 = 1.800	N2 = 1.52200	ν2 = 52.20
	r4* = −104.899

d4 = 1.553˜3.953˜1.483

	r5 = −20.000
		d5 = 0.800	N3 = 1.63854	ν3 = 55.45
	r6 = 10.131
		d6 = 1.135
	r7 = 13.404
		d7 = 2.000	N4 = 1.84666	ν4 = 23.78
	r8 = 61.168

d8 = 10.984˜3.778˜1.000

	r9 = ∞(ST)
		d9 = 0.600
	r10 = 11.382
		d10 = 2.046	N5 = 1.77250	ν5 = 49.77
	r11 = −52.132
		d11 = 0.100
	r12 = 7.001
		d12 = 2.783	N6 = 1.75450	ν6 = 51.57
	r13 = −24.543
		d13 = 0.010	N7 = 1.51400	ν7 = 42 83
	r14 = −24.543
		d14 = 0.700	N8 = 1.84666	ν8 = 23.78
	r15 = 6.105
		d15 = 1.361
	r16* = −22.829
		d16 = 1.641	N9 = 1.52200	ν9 = 52.20
	r17* = −17.058

d17 = 1.128˜7.052˜12.841

	r18* = −50.000
		d18 = 2.800	N10 = 1.74330	ν10 = 49.22
	r19 = −10 303

d19 = 2.359˜1.241˜0.700

	r20 = ∞
		d20 = 2.000	N11 = 1.51680	ν11 = 64.20
	r21 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.19527 × 10−3, A6 = 0.57342 × 10−8,

A8 = −0.20853 × 10−6

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = −0.17096 × 10−3, A6 = −0.10072 × 10−4,

A8 = −0.10753 × 10−6

Aspherical Surface Data of Surface r16

ε = 1.0000, A4 = −0.13142 × 10−2, A6 = 0.94352 × 10−4,

A8 = −0.12279 × 10−5

Aspherical Surface Data of Surface r17

ε = 1.0000, A4 = 0.11300 × 10−3, A6 = 0.11926 × 10−3,

A8 = −0.60390 × 10−7

Aspherical Surface Data of Surface r18

ε = 1.0000, A4 = −0.50806 × 10−3, A6 = 0.29779 × 10−5,

A8 = −0.38526 × 10−7

TABLE 5
Construction Data of Example 5
f = 4.8˜9.7˜15.5, FNO = 2.83˜2.85˜3.01,
2ω = 72.6˜36.8˜23.5

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 11.104
		d1 = 0.800	N1 = 1.74330	ν1 = 49.22
	r2 = 6.378
		d2 = 2.300
	r3* = 14.802
		d3 = 1.800	N2 = 1.52200	ν2 = 52.20
	r4* = 20.396

d4 = 2.430˜5.010˜4.866

	r5 = −20.000
		d5 = 0.800	N3 = 1.63854	ν3 = 55.45
	r6 = 9.907
		d6 = 0.800
	r7 = 10.952
		d7 = 1.500	N4 = 1.84666	ν4 = 23.78
	r8 = 27.854

d8 = 11.584˜3.183˜1.000

	r9 = ∞(ST)
		d9 = 0.600
	r10 = 16.003
		d10 = 1.787	N5 = 1.77250	ν5 = 49.77
	r11 = −34.803
		d11 = 0.100
	r12 = 6.218
		d12 = 2.784	N6 = 1.75450	ν6 = 51.57
	r13 = −93.239
		d13 = 0.010	N7 = 1.51400	ν7 = 42.83
	r14 = −93.241
		d14 = 0.700	N8 = 1.84666	ν8 = 23.78
	r15 = 5.710
		d15 = 1.002
	r16 = 11.201
		d16 = 1.500	N9 = 1.52200	ν9 = 52.20
	r17* = 16.808

d17 = 1.180˜7.784˜13.237

	r18* = −50.000
		d18 = 1.000	N10 = 1.58340	ν10 = 30.23
	r19* = −55.066
		d19 = 0.515
	r20 = 37.772
		d20 = 1.500	N11 = 1.78590	ν11 = 43.93
	r21 = −20.359

d21 = 1.609˜0.825˜0.700

	r22 = ∞
		d22 = 2.000	N12 = 1.51680	ν12 = 64.20
	r23 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = −0.68378 × 10−4, A6 = 0.91459 × 10−5,

A8 = −0.17059 × 10−6

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = −0.30623 × 10−3, A6 = 0.77956 × 10−5,

A8 = −0.26508 × 10−6

Aspherical Surface Data of Surface r17

ε = 1.0000, A4 = 0.15313 × 10−2, A6 = 0.48360 × 10−4,

A8 = 0.33469 × 10−5

Aspherical Surface Data of Surface r18

ε = 1.0000, A4 = 0.33814 × 10−2, A6 = −0.12472 × 10−3,

A8 = 0.45839 × 10−5

Aspherical Surface Data of Surface r19

ε = 1.0000, A4 = 0.39759 × 10−2, A6 = −0.12370 × 10−3,

A8 = 0.47201 × 10−5

TABLE 6
Construction Data of Example 6
f = 3.0˜5.2˜8.6, FNO = 2.30˜3.18˜4.10,
2ω = 76.7˜46.2˜28.2

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 18.376
		d1 = 0.750	N1 = 1.75450	ν1 = 51.57
	r2 = 5.908

d2 = 2.654˜5.660˜2.654

	r3* = −38.428
		d3 = 0.750	N2 = 1.52510	ν2 = 56.38
	r4* = 3.454
		d4 = 1.298
	r5 = 6.786
		d5 = 2.177	N3 = 1.58340	ν3 = 30.23
	r6 = −250.470

d6 = 9.631˜2.374˜1.000

	r7 = ∞(ST)
		d7 = 0.600
	r8 = 4.468
		d8 = 4.230	N4 = 1.76822	ν4 = 46.58
	r9 = −5.283
		d9 = 0.010	N5 = 1.51400	ν5 = 42.83
	r10 = −5.283
		d10 = 0.750	N6 = 1.84666	ν6 = 23.82
	r11* = 12.622

d11 = 2.573˜6.824˜11.205

	r12 = −17.607
		d12 = 1.478	N7 = 1.52510	ν7 = 56.38
	r13* = −5.316
		d13 = 0.500
	r14 = ∞
		d14 = 3.400	N8 = 1.51680	ν8 = 64.20
	r15 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = −0.22743 × 10−3, A6 = 0.81018 × 10−4,

A8 = −0.11992 × 10−4

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = −0.34914 × 10−2, A6 = −0.12871 × 10−3,

A8 = −0.99555 × 10−5

Aspherical Surface Data of Surface r11

ε = 1.0000, A4 = 0.47689 × 10−2, A6 = 0.18896 × 10−3,

A8 = 0.77520 × 10−4

Aspherical Surface Data of Surface r13

ε = 1.0000, A4 = 0.26471 × 10−2, A6 = −0.51516 × 10−4,

A8 = 0.18942 × 10−5

TABLE 7
Construction Data of Example 7
f = 2.5˜4.8˜7.3, FNO = 2.37˜3.33˜4.10,
2ω = 72.9˜40.4˜26.7

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 16.241
		d1 = 0.800	N1 = 1.75450	ν1 = 51.57
	r2 = 5.499

d2 = 3.085˜5.394˜3.085

	r3* = 23.072
		d3 = 1.000	N2 = 1.52510	ν2 = 56.38
	r4* = 3.156
		d4 = 1.390
	r5 = 5.079
		d5 = 1.653	N3 = 1.84666	ν3 = 23.82
	r6 = 7.886

d6 = 9.655˜3.023˜1.879

	r7 = ∞(ST)
		d7 = 0.600
	r8 = 4.268
		d8 = 3.824	N4 = 1.73299	ν4 = 52.32
	r9 = −5.710
		d9 = 0.010	N5 = 1.51400	ν5 = 42.83
	r10 = −5.710
		d10 = 0.750	N6 = 1.84666	ν6 = 23.82
	r11* = 27.698

d11 = 1.576˜5.899˜9.351

	r12 = −12.089
		d12 = 2.546	N7 = 1.52510	ν7 = 56.38
	r13* = −4.510
		d13 = 0.500
	r14 = ∞
		d14 = 3.400	N8 = 1.51680	ν8 = 64.20
	r15 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 0.11334 × 10−2, A6 = 0.83390 × 10−4,

A8 = −0 24186 × 10−4

Aspherical Surface Data of Surface r4

ε 1.0000, A4 = −0.14398 × 10−2, A6 = −0.68030 × 10−4,

A8 = −0.49071 × 10−4

Aspherical Surface Data of Surface r11

ε = 1.0000, A4 = 0.43753 × 10−2, A6 = 0.23651 × 10−3,

A8 = 0.47406 × 10−4

Aspherical Surface Data of Surface r13

ε = 1.0000, A4 = 0.35646 × 10−2, A6 = −0.42883 × 10−4,

A8 = 0.14875 × 10−5

TABLE 8
Construction Data of Example 8
f = 1.6˜3.0˜4.6, FNO = 2.44˜3.37˜4.10,
2ω = 76.4˜43.8˜28.8

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 7.967
		d1 = 0.800	N1 = 1.75450	ν1 = 51.57
	r2 = 3.205

d2 = 2.923˜4.841˜3.019

	r3* = 14.015
		d3 = 1.000	N2 = 1.52510	ν2 = 56.38
	r4* = 2.338
		d4 = 2.084
	r5 = 5.334
		d5 = 3.470	N3 = 1.84666	ν3 = 23.82
	r6 = 8.028

d6 = 7.717˜2.047˜1.000

	r7 = ∞(ST)
		d7 = 0.600
	r8 = 4.296
		d8 = 3.644	N4 = 1.76050	ν4 = 50.55
	r9 = −4.200
		d9 = 0.010	N5 = 1.51400	ν5 = 42.83
	r10 = −4.200
		d10 = 0.750	N6 = 1.84666	ν6 = 23.82
	r11* = −159.225

d11 = 0.897˜4.648˜7.518

	r12 = −8.166
		d12 = 2.207	N7 = 1.52510	ν7 = 56.38
	r13* = −3.963
		d13 = 0.500
	r14 = ∞
		d14 = 3.400	N8 = 1.51680	ν8 = 64.20
	r15 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.19149 × 10−2, A6 = 0.14015 × 10−2,

A8 = −0.37347 × 10−3, A10 = 0.31010 × 10−4

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = −0.67645 × 10−2, A6 = −0.60143 × 10−4,

A8 = −0.46412 × 10−3

Aspherical Surface Data of Surface r11

ε = 1.0000, A4 = 0.37565 × 10−2, A6 = 0.66871 × 10−3,

A8 = −0.80434 × 10−4

Aspherical Surface Data of Surface r13

ε = 1.0000, A4 = 0.52954 × 10−2, A6 = −0.75580 × 10−3,

A8 = 0.15734 × 10−3

TABLE 9
Construction Data of Example 9
f = 4.5˜7.8˜12.7, FNO = 3.24˜3.09˜4.13,
2ω = 76.4˜47.9˜29.6

	Radius of	Axial	Refractive	Abbe
	Curvature	Distance	Index	Number
	r1 = 21.240
		d1 = 1.200	N1 = 1.75450	ν1 = 51.57
	r2 = 5.872

d2 = 3.000˜8.500˜4.979

	r3* = 8.946
		d3 = 1.000	N2 = 1.62112	ν2 = 57.62
	r4* = 4.431
		d4 = 2.156
	r5 = 7.067
		d5 = 2.000	N3 = 1.84666	ν3 = 23.82
	r6 = 9.677

d6 = 11.453˜2.003˜1.000

	r7 = ∞(ST)
		d7 = 0.600
	r8* = 5.559
		d8 = 1.675	N4 = 1.57965	ν4 = 60.49
	r9 = 13.046
		d9 = 0.100
	r10 = 6.192
		d10 = 2.500	N5 = 1.48749	ν5 = 70.44
	r11 = −11.918
		d11 = 0.203
	r12 = −14.208
		d12 = 3.421	N6 = 1.79850	ν6 = 22.60
	r13* = 21.481
		d13 = 0.780
	r14 = 14.579
		d14 = 4.000	N7 = 1.75450	ν7 = 51.57
	r15* = 12.388

d15 = 1.898˜5.848˜10.372

	r16 = ∞
		d16 = 2.000	N8 = 1.51680	ν8 = 64.20
	r17 = ∞

Aspherical Surface Data of Surface r3

ε = 1.0000, A4 = 0.13577 × 10−2, A6 = −0.10949 × 10−3,

A8 = 0.37797 × 10−5

Aspherical Surface Data of Surface r4

ε = 1.0000, A4 = 0.65141 × 10−3, A6 = −0.18413 × 10−3,

A8 = 0.34984 × 10−5

Aspherical Surface Data of Surface r8

ε = 1.0000, A4 = −0.30607 × 10−3, A6 = −0.12679 × 10−4,

A8 = −0.66500 × 10−6

Aspherical Surface Data of Surface r13

ε = 1.0000, A4 = 0.28699 × 10−2, A6 = 0.29442 × 10−5,

A8 = 0.14242 × 10−4

Aspherical Surface Data of Surface r15

ε = 1.0000, A4 = −0.73341 × 10−3, A6 = 0.14643 × 10−3,

A8 = −0.36100 × 10−5

TABLE 10
Actual Values of Conditional Formulae

			(3)	(4)	(5) Y = 0.7 Ymax	(6)
	(1)	(2)	(tanωw)2 ·	TLw□Fnt/	(|X| − |X0|)/	(CR1 − CR2)/	(7)
Ex.	f1/f2	|f12/fw|	fw/TLw	(fw · tanωw)	[C0(N′ − N)f3]	(CR1 + CR2)	|f12/f3|

1	2.620	2.482	0.065	34.43	−0.267	0.676	1.024
2	1.434	2.416	0.068	33.65	−0.094	—	1.042
3	1.426	2.140	0.068	33.71	−0.199	—	0.974
4	1.131	2.270	0.067	34.19	−0.023	0.658	1.017
5	0.773	2.315	0.066	33.59	−0.091	—	1.203
6	1.443	2.268	0.059	55.29	−0.033	0.054	0.873
7	1.337	2.260	0.043	69.95	−0.090	0.457	0.817
8	1.269	2.206	0.032	101.59	−0.069	0.347	0.590
9	3.909	1.812	0.071	46.08	0.002	—	1.023

Claims (20)

What is claimed is:

1. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power;

wherein the third lens unit has an aspherical surface at the image side thereof; and

wherein the following conditional formulae are fulfilled:

−0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0

0.1Ymax≦Y≦0.7Ymax

wherein

X represents a surface shape of the aspherical surface;

X0 represents a surface shape of a reference spherical surface of the aspherical surface;

C0 represents a curvature of the reference spherical surface of the aspherical surface;

N represents a refractive index for a d-line of the object-side medium of the aspherical surface;

N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface;

f3 represents a focal length of the third lens unit;

Ymax represents a maximum effective optical path of an aspherical surface; and

Y represents a height in a direction perpendicular to an optical axis.

2. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power and provided at the most object side of the zoom lens system, a second lens unit having a negative optical power, and a third lens unit having a positive optical power, and

wherein the following conditional formula is fulfilled:

0.5<f1/f2<5

wherein

f1 represents a focal length of the first lens unit; and

f2represents a focal length of the second lens unit.

3. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power; and

wherein the following conditional formulae are fulfilled:

1.5<|fl2/fw|<4

0.058<(tan ωw)² ×fw/TLw<0.9

wherein

fl2 represents a composite focal length of the first and the second lens units at a wide-angle end;

tan ωw represents a half view angle at a wide-angle end;

fw represents a focal length of an entire optical system at the wide-angle end; and

TLw represents a distance from a first vertex to an image plane at the wide-angle end.

4. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power; and

wherein the following conditional formulae is fulfilled:

1.5<|fl2/fw|<4

10<TLw×Fnt/(fw×tan ωw)<50

where

TLw represents a distance from a first vertex to an image plane at a wide-angle end;

Fnt represents an f-number at a telephoto end;

fl2 represents a composite focal length of the first and the second lens units at the wide-angle end;

fw represents a focal length of an entire optical system at the wide-angle end; and

tan ωw represents a half view angle at the wide-angle end.

5. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power and provided at the most object side of the zoom lens system, a second lens unit having a negative optical power, and a third lens unit having a positive optical power, and

wherein the lens unit closest to the image side has a positive optical power, said lens unit is comprised of at least one positive lens element and the positive lens element fulfills the following conditional formula:

0.05<(CR1−CR2)/(CR1+CR2)<5

wherein

CR1 represents a radius of curvature of the object-side surface; and

CR2 represents a radius of curvature of the image-side surface.

6. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, and a third lens unit having a positive optical power; and

wherein the following conditional formula is fulfilled:

04<|fl2/f3|<1.5

where

fl2 represents a composite focal length of the first and the second lens units at a wide-angle end; and

f3 represents a focal length of the third lens unit.

7. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power and provided at the most object side of the zoom lens system, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power; and

wherein said first lens unit through said fourth lens unit are disposed sequentially across a variable air gap.

8. An optical device as claimed in claim 7 wherein the zoom lens system achieves zooming by varying distances between the first lens unit to the fourth lens unit.

9. An optical device as claimed in claim 8 wherein the zoom lens system further comprises a low-pass filter which adjusts spatial frequency characteristics of the optical image formed by the zoom lens system, said low-pass filter located between the first lens unit and the image sensor.

10. An optical device as claimed in claim 9 wherein the first lens unit and the low-pass filter remain stationary during zooming.

11. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power and being provided at the most object side of the zoom lens system, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power; and

wherein the first lens unit is a single lens element.

12. An optical device as claimed in claim 7 wherein the first lens unit comprises two lens elements.

13. An optical device as claimed in claim 7 wherein the third lens unit comprises at least two positive lens elements and at least one negative lens element.

14. An optical device as claimed in claim 7 wherein the third lens unit has an aspherical surface at the image side thereof.

15. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power;

wherein the third lens unit has an aspherical surface at the image side thereof; and

wherein the following conditional formulae is fulfilled:

−0.6<(|X|−|X0|)/[C0·(N′−N)·f3]<0

0.1Ymax≦Y≦0.7Ymax

wherein

X represents a surface shape of the aspherical surface;

X0 represents a surface shape of a reference spherical surface of the aspherical surface;

C0 represents a curvature of the reference spherical surface of the aspherical surface;

N represents a refractive index for a d-line of the object-side medium of the aspherical surface;

N′ represents the refractive index for the d-line of the image-side medium of the aspherical surface;

f3 represents a focal length of the third lens unit;

Ymax represents a maximum effective optical path of an aspherical surface; and

Y represents a height in a direction perpendicular to an optical axis.

16. An optical device as claimed in claim 7 wherein the following conditional formula is fulfilled:

0.5<f1/f2<5

wherein

f1 represents a focal length of the first lens unit; and

f2 represents a focal length of the second lens unit.

17. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power; and

wherein the following conditional formulae are fulfilled:

1.5<|fl2/fw|<4

0.058<(tan ωw)2×fw/TLw<0.9

wherein

fl2 represents a composite focal length of the first and the second lens units at a wide-angle end;

tan ωw represents a half view angle at a wide-angle end;

fw represents a focal length of an entire optical system at the wide-angle end; and

TLw represents a distance from a first vertex to an image plane at the wide-angle end.

18. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power; and

wherein the following conditional formulae is fulfilled:

1.5<|fl2/fw|<4

10<TLw×Fnt/(fw×tan ωw)<50

where

TLw represents a distance from a first vertex to an image plane at a wide angle end;

Fnt represents an f-number at a telephoto end;

fl2 represents a composite focal length of the first and the second lens units at the wide-angle end;

fw represents a focal length of an entire optical system at the wide-angle end; and

tan ωw represents a half view angle at the wide-angle end.

19. An optical device as claimed in claim 7 wherein the lens unit closest to the image side has a positive optical power, said lens unit is comprised of at least one positive lens element and the positive lens element fulfills the following conditional formula:

0.05<(CR1−CR2)/(CR1+CR2)<5

wherein

CR1 represents a radius of curvature of the object-side surface; and

CR2 represents a radius of curvature of the image-side surface.

20. An optical device comprising:

a zoom lens system, comprising a plurality of lens units, which achieves zooming by varying unit-to-unit distances; and

an image sensor for converting an optical image formed by the zoom lens system into an electrical signal,

wherein the zoom lens system comprises at least, from an object side thereof to an image side thereof, a first lens unit having a negative optical power, a second lens unit having a negative optical power, a third lens unit having a positive optical power, and a fourth lens unit having a positive optical power; and

wherein the following conditional formula is fulfilled:

0.4<|fl2/f3|<1.5

where

fl2 represents a composite focal length of the first and the second lens units at a wide-angle end; and

f3 represents a focal length of the third lens unit.

Images